In many respects, the interface between computers and the physical world including people remains quite crude.
Many present input and interface media are not constructed to be used in a particularly rich or natural manner. For example, digitizing tablets often make use of special pens which necessarily constrain the quantity and quality of the information input through them (i.e. simple lines of uniform width and intensity). While for some circumstances such input devices are adequate, in many cases a more general tactile interface is desired.
Tactile sensors, i.e. sensors involving transducers which convert pressure (i.e. touch) information into electrical signals, have previously been constructed based upon several physical principles. Among these are the use of piezoresistivity, piezoelectricity, and capacitive sensing to measure the local force applied to a substrate.
Tactile capacitive sensor arrays have been disclosed in a number of U.S. Patents, such as, for example only, U.S. Pat. Nos. 5,016,008; 4,731,694; 4,740,781; 4,431,882; and 4,614,937. Such known arrangements do not generally have fine spatial resolution capabilities, and employ passive addressing systems that require the provision of addressing conductors on two separate substrates which must be aligned. This latter arrangement makes it especially difficult to fabricate large sensor arrays of high spatial resolution. In addition, it is difficult, in known capacitive sensor arrays, to provide outputs that are responsive to the degree of pressure applied to the capacitive sensor pads.
A large number of designs for creating arrays of capacitive cells have been discussed in the literature. (See, for example, "A High-Performance Silicon Tactile Imager Based on a Capacitive Cell", K. Chun and K. D. Wise, IEEE Transactions on Electron Devices, ED-32 (7), pp. 1196-1201 (1985); "A 1024-Element High-Performance Silicon Tactile Imager", K. Suzuki, K, Najafi, and K. D. Wise, IEDM, pp. 674-677 (1988); "128.times.128 Deformable Mirror Device", L. J. Hornbeck, IEEE Transactions on Electron Devices, ED-30 (5), pp. 539-545 (1983); and "Deformable mirror device spatial light modulators and their applicability to optical neural networks", D. R. Collins, et al. Applied Optics, 28(22), pp. 4900-4913 (1989)). In deformable mirror devices (DMDs), voltages are applied to one plate of each capacitive cell (each electrode on the glass substrate), to produce a deformation of the bridge or cantilever, which in turn will scatter an optical beam incident on the array. There has been no demonstration, however, that any of these arrangements can be made to have large areas.